1. Field of Invention
The present invention relates to control methods and systems for controlling fueling of an engine in a vehicular automated mechanical transmission system after completion of a non-power downshift. In particular, the present invention relates to controlling of fueling of an electronically controlled engine (preferably of the type associated with an SAE J 1922 or SAE J 1939 protocol data link) in a vehicular automated mechanical transmission system (preferably of the type shifted without disengagement of the master clutch) during the period of time from completion of jaw clutch engagement of a non-power downshift until control of engine fueling is determined solely by operator positioning of the throttle device.
2. Description of the Prior Art
Fully or partially automated vehicular control systems wherein, for a period of time, fueling of the vehicular engine is controlled by the system controller (usually a microprocessor-based controller), regardless of operator throttle pedal positioning, are well known in the prior art. Examples of such systems include automated transmission systems, traction control systems, anti-lock brake systems and the like. Control strategies for returning control of engine fueling to the operator (i.e., "throttle recovery") also are known in the prior art. See, for example, U.S. Pat. No. 4,792,901, the disclosure of which is incorporated herein by reference.
Fully or semi-automatic transmission systems utilizing electronic control units which sense engine fueling, throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement selected transmission ratio changes are known in the prior art. Examples of such automated mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated transmission system provides semi-automatic shift implementation for a mechanical transmission system for use in vehicles having an electronically controlled engine and a manually only controlled master clutch. An electronic control unit (ECU) is provided for receiving various signals, such as input signals indicative of transmission input and output shaft speeds, and for processing same in accordance with predetermined logic rules to issue command output signals to an engine fueling controller and a transmission actuator for shifting the transmission in accordance with the command output signals. Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; and 5,089,965, the disclosures of which are hereby incorporated by reference.
Electronically controlled engines are known and typically provide information to and receive command requests from a data link of the type conforming to the European "CAN" protocol and/or the SAE J 1922 or SAE J 1939 protocol. Such engines have four modes of operation wherein engine fueling is adjusted to:
(1) follow the operator's setting of the throttle device (usually a pedal);
(2) to cause engine torque to equal a requested engine torque;
(3) to cause engine speed to equal a requested engine speed; or
(4) to cause engine speed and engine torque to be limited to requested engine speed and torque values,
The above modes usually are referred to as the throttle tracking mode, the torque control mode, the speed control mode, and the torque and speed limiting mode, respectively.
While the prior art automated mechanical transmission systems of the type including electronically controlled engines and having a mode of operation wherein shifts are performed without disengagement of the master clutch are generally satisfactory, they were not totally satisfactory, as after the completion of a shift, throttle recovery was attempted by causing the engine to achieve a requested torque, which provided very high quality shifts for upshifts and power downshifts but which tended to cause roughness and/or cab lurch after a non-power downshift (i.e., a downshift when throttle pedal is at or near minimal setting, preferably less than 5-percent displacement).